Electric fuse and method of manufacture thereof



.lIune 29, 1954 N, o. BURT ET AL ELECTRIC FUSE AND METHOD OF MANUFACTURE THEREOF Filed March 12, 1949 Patented June 29, 1954 ELECTRIC FUSE AND METHOD OF MANUFACTURE THEREOF Nelson 0. Burt, Larchmont, and August P.

J urgensen, New York, N. Y., assignors to General Fuse Company, Jersey City, N. J., a corporation of New Jersey Application March 12, 1949, Serial No. 81,138

3 Claims.

This invention relates to improvements in electric fuses and methods of manufacture thereof, and more particularly to electric fuses and methods of manufacturing electric fuses of the glasstube cartridge-type.

Conventional electric fuses of the glass-tube cartridge-type heretofore have individually been formed of a casing composed of an insulating glass tube provided with a metallic end-cap or ferrule secured at each end, and having fuse links mounted within said glass tube and connected at its opposite terminal ends by soldered joints to the internal bottom surfaces of the metallic caps or ferrules. Such fuse links, though sometimes provided with radially-extending shoulders, have heretofore been positioned to extend longitudinally along the axis of the tube and caps, and have been straight and unyielding in a lengthwise direction. Consequently, when the solder of the soldered joints between the ends of the link and the metallic caps cools and hardens and therefore contracts, the fuse-link is subjected to tension and becomes taut or stretched tightly between such soldered joints. This tightstretching and tensioning are undesirable characteristics that result in link fracture when the fuse is subjected to rough handling or shock, and one of the objects of our invention is to eliminate and avoid such undesirable characteristics in our fuse link and to provide a fuse in which the fuse link, after soldering of the ends, will be yielding and untensioned axially or in a lengthwise direction and, instead of extending longitudinally along the axis of the tube, will embody one or more yieldable longitudinally-bent portions which cross the longitudinal axis of the tube While still positioning the fusible portion of the link in proper position, thus producing a fuse-link that will withstand much greater abusive strains and rough handling than conventional fuse links.

Another object of our invention is in a fuse of the character specified to provide a fuse link construction comprising an intermediate fusible portion and terminal sections at opposite ends thereof, provided with a yieldable bent portion or portions embodied therein and preferably each terminal section is provided at opposite ends of said fusible portion with a yieldable bend or bent portion.

Another object of our invention is in a fuse of the character specied to produce a fuse-link having at the middle thereof a fusible portion and integral terminal sections extending to opposite ends of said link, and to provide in each of such integral terminal sections a yieldable (Cl. 20G-131) 2 bend or bent portion so disposed in relation to the fusible portion that they Will cause the fusible portion to be positioned unfailingly in substantially equally-spaced relationship to the inside surface of the glass tube and preferably to be so positioned at the middle of the tube as to cross the longitudinal axis at a slightly inclined angle.

Another object of our invention is to provide in that part of each of the integral terminal seetions which extends within and above the rim of the cap a yieldable bent portion which extends in an opposite directionffrom its counterpart in the opposite terminal section so that the Visible portion of the link, including parts of the terminal portions and the fusible portion, will be disposed diagonally at a slight angle from the vertical across the longitudinal axis of the tube at the middle thereof, and because of said yieldable bent portions variations in the lengths of the glass tubes and links will not materially affect the centralizing of the fusible portion of the link.

Still another object of our invention is in a fuse of the character specied to improve prior art practice which forms a solder-joint between a straight, narrow fuse end and ay perpendicularly-extending contacting portion of the cap by producing a fuse link having a more secure solder joint between the ends of the link and the contact portions of the caps or ferrules than has heretofore been possible in such prior art practice, and, with these ends in view, We provide each tip end of the terminal sections with a contactforming integral bend, one of which bends preferably extends in an opposite direction to the other at a right angle to the said longitudinal axis and in iinal position extends substantially parallel with the link-contacting portion of the metallic cap, thus producing at each end of the link a wide solder-embedded base.

Another object of our invention is to position the yieldable bends in the said integral terminal sections adjacent to the caps and in continuity with said contact forming bends so as to cause the fuse link to cross the longitudinal axis in opposite directions and to cause the fusible portion thereof to be also placed in a slightly-inclined position across the said axis at the middle portion of the tube.

With these and other objects in view, the invention comprises the combination of members and arrangementof parts so combined as to coact and cooperate with each other in the performance of the functions and the accomplishment of the results herein contemplated, and comprises in one of its adaptations the species or preferred form illustrated in the accompanying drawings, in which:

Fig. 1 is a view in side elevation of an electric fuse embodying my invention;

Fig. 2 is a longitudinal section on the line 2 2 of Fig. l, looking in the direction of the arrows;

Fig. 3 is a cross-section on the line 3-3 of Fig. 2, looking in the direction of the arrows;

Fig. 4 is a longitudinal section at a right angle i to Fig. 2 and on the line 4-4 of Fig. 2 looking in the direction of the arrows;

Fig. 5 is a longitudinal section of a tube having a cap at one end with a yblock of solder loosely supported in the cap, the section being similar to Fig. 2 and substantially on the line 2-2 of Fig. 1

Fig. 6 is a section similar and in continuing sequence to Fig.` 5 showing the block of soldei melted to form a soldered joint between one end of the fuse link and the metallic cap;

Fig. 7 is another section similar and in continuing sequence with Figs. 5 and 6 showing a partly finished fuse invertedA and a block of solder positioned within a partly-mounted cap applied to the lower, opposite end;

Fig. 8 is another sequential section similar to Figs. 5 to 7 and showing a soldered joint formed after heat has been applied to the loose block of solder in Fig. 7;

Fig. 9 is a view in side elevation of a straight blank for the preferred form of fuse link employed by us;

Fig. i0 is an edge elevation of the fuse link shown in Fig. 9 after the same has been initially bent into the form shown in Fig. 5; and

Figs. 11 to 13 respectively are modified forms of fuse links capable of' use in our device.

Referring now to Figs. 1 to 10 of these drawings which illustrate a preferred embodiment of and also has, at opposite sides of said fusible portion, terminal sections IIL-I5a embodying yieldable bends or bent-portions preferably extending to opposite sides of the longitudinal axis of the tube.

In the preferred form of our invention, the

fuse link is provided with double yielding or i .Yieldable bends I6, I6'L extending in opposite directions, each of the terminal4 sections I5, I5a o preferably also cause positioning of said fusible portion at precisely the middle portion of the tube.

In the preferred embodiment of our invention, the apicesvof said oppositely-directed yieldable bent portions are preferably positioned within the caps or registering with the rims l2@ thereof so that the visible body portion of the link, including visible parts of the terminal sections and the fusible portion, will be disposed and extend in a long line diagonally across the longitudinal axis of the tube with the fusible portion at the middle thereof and because of these yieldable bends any variation in the length of the glass tubes will not materially affect the centralizing of lthe fusible portion of the link.

As illustrated, the bends I6, Ilia in the terminal sections I5, Ia are resilient or articulating and in said preferred embodiment are, as aforesaid, preferably positioned to cause the apex of the bend to substantially register with the rim of the metallic cap, so that when such resilient or articulating bends are provided in the terminal sections, the intermediate body part of the link containing the fusible portion thereof will extend between the parts that are bendable at the outer sides of the apices and in the preferred embodiment of our invention this body part, which is visible, will extend diagonally across the axis of the tube and will cause said fusible portion at the middle of the fuse link to be po sitione-d substantially at the axis of the tube and also in substantially equally spaced relationship to the inside surface of said glass tube II, while at the same time a fuse link will be produced that will be adapted under tension and during a cooling and hardening of the solder in soldered joints to yield or articulate slightly, and thus eliminate the conventional placing of the fused links under tension during the cooling of solder after the soldering operation. Ceriseduently we avoid the brittleness of prior art fused links that are so placed under tension through the cooling of solder in the necessary soldered joints at opposite ends thereof.

In addition to the yelding or articulating bends Iii-46a, We also preferably provide our pre ferred form of fused link with oppositelydirect ed tip end bends I1, VIa which are adapted to provide at the tip ends relatively wide solderembedded base plates Ill, iiiil adapted to lie flat against the bottom contact-portions IZb--IZh of the metallic caps or ferrules and to form with such bottom portions of the cap flat contact surfaces, and in the preferred form of our invention these fiat contact surfaces are soldered to the contact portions of end caps by solder joints I9, I9a which secure together the said flatly engaged contact surfaces to provide a more secure joint than would be otherwise possible.

In the operations of applying the fuse link to the fuse casing, the lower metallic cap is first placed in position on the glass tube, a block of solder is then dropped into contact with the contact portion of a metallic cap or fer-rule, a fuse link with the bends I 6, 16a in final bent relationship but with the ends I1 in partly bent form is then dropped into the tube. The plates I8 will still be arranged at a greater angle than the nnal position thereof in this initially-dropped position but the lower end of the plate will contact with a block of solder. Heat is then applied beneath said metal cap I2 in any suitable manner to melt the solder and simultaneously the link is pressed downwardly to cause the plato IB* to assume the position shown in Fig. 6, whereupon a secure soldered joint with the Contact portion of one of the metallic caps I2, such as shown at I9 in Fig. 6, is produced, the contact base plate at the opposite upper end being also moved into nal position as shown` in said Fig.

6. The fuse-casing is then inverted into the position shown in Fig. 7, a block of solder I9a is positioned Within a cap I2 which is partially mounted in telescoped relationship with the tube II. Heat is then applied beneath said cap I2 to melt the block of solder I9a and simultaneously pressure is applied to produce a second soldered joint I9 and to move the cap I2 into its final position as shown in Fig. 8.

In Fig. 9 I have shown a suitable blank for a fusible link such as shown in Figs. 1 to 8 and this blank is preferably provided at opposite ends with circular heads which, in final position, form the plates I8. This blank has at the middle thereof a fusible portion I4 and terminal sections I5, I5@ which, as shown in Fig. 10, are bent to provide the yielding or articulating bent portions I6, IE5ab and the contact plates I8 which are also bent above the axis I'I.

In the preferred embodiment of our invention, the metallic blank or strip is provided at opposite sides with indentations Id,` I8d to enable a more facile bending of the contact plate I8 in relation to the body of the fusible link.

In Fig. 11, we have shown a blank for a modi fied form of fusible link which is in all respects similar to the fusible link in Fig. 9 except that instead of providing rounded contact plates i3 the contact plates I8b are rectangular and holes I8c are provided between the contact plates in the body of the fusible link to assist in facile bending of the plates I8b.

In Fig. 12 we have shown still another form of blank which is likewise in all respects similar to the link shown in Fig. 9 except that the fusible portion I lIa is straight instead of diagonally arranged as shown in Figs. 1-4 and 9.

In Fig. 13 we have shown still another modified form of our blank for a fusible link in which the fusible link portion IIIb is shorter than the link shown in Fig. 11 and the holes I3c are omitted. In other respects the construction shown in Fig. 13 is the same as that illustrated in Fig. 11.

Having described our invention, we claim:

1. An electric fuse comp-rising, in combination, a tube of insulating material, a metallic cap covering and enclosing each end thereof, a link within said tube having a fusible portion substantially at its middle, said link having bent substantially parallel tip ends `adapted to rest against the inside of the covers of the metallic caps respectively, a fused electrical connection anchoring said parallel tip ends respectively to the insides of the covers of the caps, the end portions 'of said link being bent acute angularly in opposite directions from said tip ends to an intermediate portion connected with each end portion by an apex forming an obtuse angle, each apex being in substantial engagement with the inner Wall of the'tube for substantially centering the fusible portion thereof, and the intermediate portion extending at an angle to the axis of the tube so that contraction of the link results in bending which minimizes tension on the fusible portion.

2. An electric fuse comprising, in combination,

a fuse casing composed of a tube of insulating" allel to and contacting with a major part of the inside cover portion of a metallic cap, each cap cover portion and tip-end being provided with a fused electrical connection securely anchoring said tip end to the inside of the adjacent cover, said fuse-link comprising outer terminal sections connected with said tip end portions at opposite sides of the axis of the tube and extending across said axis to the opposite sides thereof and being connected integrally with an intermediate section having a middle fusible portion, each tip end portion and adjacent outer terminal section forming an acute angle, and the intermediate section and each outer terminal section forming an obtuse angle having its apex in substan tial engagement with the inner Wall of the tube whereby the fusible portion of the intermediate section is substantially centered in the tube and whereby contraction of the fuse-link results in bending which minimizes tension on the fusible portion.

3. An electric fuse comprising, in combination, a fuse-casing composed of a tube of insulating material and a metallic cap covering and closing each end thereof, a fuse-link having at each end an electrical contact portion comprising an angularly-bent portion of the tip-end of the fuselink positioned to contact flatly with the inner surfaces of the contact portion of the metallic caps and to be complementary to a major part of the inner end surfaces of the caps, and a soldered joint between each of said angularlybent tip-end portions and each of said contact portions of the metallic caps to anchor said tip end portions to said contact portions of said metallic caps, said fuse-link having outer end portions bent acute angularly in opposite directions from said tip-ends to an intermediate portion connected with each outer end portion by an apex forming an obtuse angle, each apex being in substantial engagement with the inner wall of the tube for substantially centering the middle of the intermediate portion in the tube,l and the intermediate portion extending at an angle to the axis of the tube so that contraction of the fuse-link results in bending which minimizes tension on said intermediate portion.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,288,724 Snelling Dec. 24, 1918 1,443,865 Bogle Jan. 30, 1923 1,734,211 Johnson Nov. 5, 1929 2,166,033 Alberga et al. July 11, 1939 2,313,373 Sundt Mar. 9, 1943 2,412,712 Brown Dec. 17, 1946 2,419,250 Brus Apr. 22, 1947 2,567,420 Bowie Sept. 11, 1951 FOREIGN PATENTS Number Country Date 941,455 France July 19, 1948 

